Phase delay circuits are widely used in a number of electric, electronic and opto-electronic environments. Digital phase delay circuits, for example, are commonly used to produce finely-controlled clock signals, modulation signals, demodulation signals and the like in a variety of settings and applications. Conventional optical phase domain reflectometer (OPDR) devices, for example, typically inject light into optical fibers under test and then measure the phasing of light reflected back from the fiber to ascertain certain characteristics (e.g. attenuation, fiber length, distance breaks in the fiber, etc.) of the fiber under test. In such devices, it is generally desirable to precisely control the phasing of the digital signals used in modulating and demodulating the light propagating in the fiber. A digital phase delay circuit may therefore be used to produce modulation and demodulation signals that are similar to each other, yet delayed very slightly in time. Many other optical, electronic and electronic devices use other forms of phase delay for widely varying purposes.
Generally speaking, engineers are continually striving to reduce the cost, weight and power consumption of various products; this is especially true in aerospace settings, as well as in homeland defense and other governmental settings. In the case of unmanned aerial vehicles (UAVs), for example, it may be desirable to deploy a number of OPDR and/or other reflectometer devices throughout the vehicle to quickly and accurately identify any breaks or other issues in optical fibers used in collision avoidance, control and/or other systems operating on the vehicle. In such settings it would be highly desirable to produce digital phase delay circuits that are not only highly accurate and programmable, but that are also relatively low-cost and efficient in terms of size, weight and power (SWAP). A low cost and low SWAP delay circuit could have wide application in numerous other devices and settings as well.